| Инд. авторы: | Sokol A.G., Palyanov Y.N., Kupriyanov I.N., Litasov K.D., Polovinka M.P. |
| Заглавие: | Effect of oxygen fugacity on the H2O storage capacity of forsterite in the carbon-saturated systems |
| Библ. ссылка: | Sokol A.G., Palyanov Y.N., Kupriyanov I.N., Litasov K.D., Polovinka M.P. Effect of oxygen fugacity on the H2O storage capacity of forsterite in the carbon-saturated systems // Geochimica et Cosmochimica Acta. - 2010. - Vol.74. - Iss. 16. - P.4793-4806. - ISSN 0016-7037. - EISSN 1872-9533. |
| Внешние системы: | DOI: 10.1016/j.gca.2010.05.032; SCOPUS: 2-s2.0-77954539489; |
| Реферат: | eng: High pressure experiments have been performed in the systems Mg2SiO4-C-O-H and Mg2SiO4-K2CO3-C at 6.3GPa and 1200 to 1600°C using a split-sphere multi-anvil apparatus. In the Mg2SiO4-C-O-H system the composition of fluid was modeled by adding different amounts of water and stearic acid. The fO2 was controlled by the Mo-MoO2 or Fe-FeO oxygen buffers. Several experiments in the Mg2SiO4-C-O-H system and all experiments in the Mg2SiO4-K2CO3-C system have been conducted without buffering the fO2. Forsterite in the system Mg2SiO4-K2CO3-C does not reveal OH absorption bands in the IR spectra, while forsterite coexisting with carbon-bearing fluid and silicate melt at logfO2 from FMQ-2 to FMQ-5 (from 2 to 5 log units below fayalite-magnetite-quartz oxygen buffer) contains 800-1850wt. ppm H2O. The maximum concentrations were detected at 1400°C and FMQ-3.5. We observed an increase in the solidus temperature in the system Mg2SiO4-C-O-H from 1200 to above 1600°C with logfO2 decreasing from FMQ-2 to FMQ-5. The increase of the solidus temperature and the broadening of the stability field of the H2O-H2-CH4 subsolidus fluid phase at 1400-1600°C explain the high H2O storage capacity of forsterite relative to that crystallized from carbon-free, oxidized, hydrous, silicic melt. At temperatures above 1400°C liquidus forsterite precipitated along with diamond from oxidized (FMQ-1) carbonate-silicate melt and from silicate melt dissolving the moderately reduced C-O-H fluid (from FMQ-2 to FMQ-3.5). Formation of diamond was not detected under ultra-reduced conditions (FMQ-5) at 1200-1600°C. Olivine co-precipitating with diamond from dry carbonate-silicate or hydrous-silicic fluid/melt can provide information on the H2O contents and speciation of the diamond-forming media in the mantle. The conditions for minimum post-crystallization alteration of olivine and its hydrogen content are discussed. © 2010 Elsevier Ltd.
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| Ключевые слова: | water; olivine; high pressure; fugacity; forsterite; fluid composition; experimental mineralogy; diamond; crystallization; |
| Издано: | 2010 |
| Физ. характеристика: | с.4793-4806 |